Previous work

My previous research (PhD project) was focused on quantifying the effects of cosmic dust on all the photometric parameters of disks and bulges of spiral galaxies, develop and provide to observers a robust and reliable method to correct for these effects. Accurate measurements of the photometric parameters are needed in various studies. For example, dust corrections of disk scale-lengths and bulge effective radii are essential in understand the assembly and evolutionary history of these systems and test predictions of the semi-analytical hierarchical models of galaxies formation (e.g the inside-out formation scenario), dust corrections are also required to remove degeneracies produced by dust in surface brightness measurements (which are part of resolved studies of stellar populations).
For this study I have used simulated images of disks and bulges, seen both in isolation or in composite systems (as galaxies), produced by means of radiative transfer calculations and the theoretical model of Popescu et al. (2011). For visualisation and analysis of all the simulated, model and residual images I used astronomical software tools like GAIA and DS9. To derive the changes in the photometric parameters from their known intrinsic values (input in the simulations) I have fitted the simulated images with parametric models (used also by observers for surface brightness photometry on real images of galaxies) - infinitely thin disks described by exponential, Sérsic or de Vaucouleurs functions. I have performed this process using GALFIT data analysis algorithm and developed a set of routines and wrappers in IDL capable to incorporate GALFIT and perform the analysis of all the images and the results obtained. Besides single or multi-component fitting using a part of the parametric functions available, I have used other features such as truncation functions (e.g. radial outer truncation), constraints on some of the photometric parameters, or azimuthal profile functions. In addition, I have also used GALFIT capabilities to create model images of disks/bulges.
This is the first time a systematic and self-consistent quantification of these effects has been performed covering the whole parameter space (in wavelength, disk inclination, central face-on B band dust opacity ( $\tau_{B}^{f}$ ) and bulge/disk ratio) and all photometric parameters of spiral galaxies and its constituent stellar components. I have done the analysis firstly for disks and bulges seen in isolation (thus quantifying dust and projection effects) and subsequently for the same morphological components seen together (thus quantifying the dust effects on bulge-disk decomposition). To test how projection and dust effects depend on the distribution of bulge volume stellar emissivity, I have simulated bulges with volume stellar emissivities described by different Sérsic distributions and truncated at different effective radii. Briefly, the results obtained show that:

• projection effects are significant for highly inclined disks, while for bulges these are independent of inclination, increase with the Sérsic index of the volume stellar emissivity and are strongly dependent of the truncation radius (Pastrav et al. 2013a);
• dust distorts all the photometric parameters of single disks/bulges, with the thin disk parameters suffering the most severe effects; dust corrections for bulges are found to be insensitive to the choice of the truncation radius and ellipticity of the bulge, and exhibit similar variations with inclination and dust opacity for bulges with different Sérsic index, with differences being observed only at close to edge-on inclinations (Pastrav et al. 2012, Pastrav et al. 2013a);
• dust effects on the photometric parameters of decomposed disks and bulges increase with the Sérsic index of bulge intrinsic volume stellar emissivity distribution and depend on the $B/D$ ratio for galaxies with higher Sérsic index bulges (Pastrav et al. 2013b).

I have tested my model predictions for wavelength dependence of dust effects on disk scale-lengths and Sérsic indices of single disks and found that these can account for the trend seen in observational data (the disks-dominated sample) coming from the GAMA (Galaxy And Mass Assembly) survey (Kelvin et al. 2012, Häußler et al. 2013). Likewise, I compared the predictions for the inclination dependence of disk and bulge sizes with observational data (SDSS - Sloan Digital Sky Survey) from a sample selected from Simard et al. (2011) and showed that on average the model can account for the trends seen in the data.
The corrections for dust effects on disk effective radii were employed by Grootes et al. (2013) to derive accurate disk scale-lengths. These in turn were used to calculate B-band face-on dust opacity ( $\tau_{B}^{f}$ ) from observable properties and to show that a correlation exists between $\tau_{B}^{f}$ and the stellar mass surface density in nearby spiral galaxies.
I made publically available (at CDS database) all the corrections for all the aforementioned effects, to be used by the interested scientific community.

Aside from this, I have used the Popescu et al. (2011) SED model on a few resolved galaxies in order to test its accuracy. In this respect, I have used the library of model SEDs for dust and PAH (polycyclic aromatic hydrocarbon) emission and corresponding dust attenuations derived in Popescu et al. (2011), together with a set of routines (that I have created in IDL) to fit the SEDs of the resolved galaxies, in order to derive parameters like star-formation rate (SFR), bulge-to-disk ratio (B/D), or the luminosities of the young and old stellar population for each galaxy. As a consequence, I have acquired a background in SED modelling and fitting techniques and become knowledgeable of the SED and dust models proposed in the literature and currently used.
During my PhD and at present, I have successfully worked in a small research team, occasionally collaborating with other researchers from MPIK (Max-Planck-Institut fuer Kernphysik, Heidelberg), UCLan and GAMA collaboration.

References

Grootes, M., Tuffs, R.J., Popescu, C.C., Pastrav, B., Andrae, E. et al. 2013, ApJ 766, 59
Kelvin, L.S., Driver, S.P., Robotham, A.S.G. et al. 2012, MNRAS, 421, 1007
Häußler, B., Bamford, S.P., Vika, M. et al. 2013, MNRAS 430, 330
Pastrav, B. A., Popescu, C. C., Tuffs, R. J., Sansom, A. E. 2012, Proceedings of the International Astronomical Union, IAU Symposium 284, eds. R. J. Tuffs & C. C. Popescu, 306
Pastrav, B. A., Popescu, C. C., Tuffs, R. J., Sansom, A. E. 2013a, A&A 553, A80
Pastrav, B. A., Popescu, C. C., Tuffs, R. J., Sansom, A. E. 2013b, A&A 557, A137
Popescu, C. C., Tuffs, R. J. et al. 2011, A&A 527, A109
Simard, L., Mendel, J.T, Patton, D.R. et al. 2011, ApJS, 196, 11